1. Field of the Invention
The present invention relates to a sealing joint for sheet piles.
2. Description of the Prior Art
Sheet piles are metallic sections having geometries of varying complexity (Z-shaped, U-shaped or flat sheet piles, for example, or joined together in a caisson), which are assembled to form continuous structures known as sheet-pile walls. Assemblies of sheet piles are used more particularly during work connected with excavation, with the construction of dams, reservoirs and basins for confinement of sewage etc., in order to retain soil and, to a certain extent, water as well.
On site, the sheet piles, which are often assembled two at a time (twinning) at the factory by what are called threading machines, are driven into the ground by ramming, by vibration or by presses to form a metallic wall by virtue of the mutual interlocking between their gripping elements or claws. A certain amount of play in the region of their gripping elements must be allowed so that the sheet piles can easily be interlocked during their assembly, and this naturally forms a source of leakage.
As soon as there is a requirement for the sheet-pile wall to be impervious, whether the imperviousness is to be perfect or as efficient as possible, additional measures must be provided for sealing the gripping elements.
Attempts have been made to seal the sheet-pile wall after being driven in, either by welding the sheet piles to each other, or by pressurised injection of a sealing mass into the interstices of the gripping elements, as described in the German patent application published under no. DE-OS-21 40 250.
These two methods are, however, applicable only if one of the two faces of the sheet-pile wall remains accessible.
If the sheet-pile wall is inaccessible, it is possible to proceed as described in the German patent application published under no. DE-OS-21 42 957 and inject into a gripping element of the sheet piles, even on site and before pile-driving, a mass which is introduced in the liquid state and which solidifies in the form of a foam with an elastic consistency.
Alternatively, it is possible to conform to the German patent application DE-AS 27 22 978, according to which a joint is formed in the gripping element to be interlinked by injecting into it a suitable product, generally polyurethane, and by smoothing out the product by means of a mobile device to give it the desired shape.
The above-mentioned sealing joints have the disadvantage that they offer little resistance to stresses during the interlocking, particularly to shearing. While the sheet piles are being driven in, the gripping elements rub against each other and the sealing joint may be destroyed, at least locally, by the joint being planed down.
The use of these polyurethane-based joints generally requires an elaborate preparation of the gripping element. In fact, it is often necessary to clean the gripping element by sand-blasting and to introduce a product to improve the adhesion of the joint to the steel. In spite of all these precautions, sheet piles incorporating this type of joint cannot be driven in by vibration, since the joints would suffer too much damage during the pile-driving.